Reducing the SD card clock speed - Raspberry Pi Forums

hi all.

designing in raspi product , trying reduce emc emissions pi. have seen in both near , far field, there 350mhz spike in spectrum. have traced harmonic of 50mhz spi clock signal. in order reduce emissions, want decrease clock signal. in config.txt, can change init_emmc_clock down 32000000 (32mhz) no further. if set lower (for example, 31000000), pi not boot, , boot terminal displays:

code: select all

mmc0: timeout waiting hardware interrupt - cmd52. mmc0: reset 0x2 never completed. mmc0: reset 0x4 never completed. timeout waiting hardware interrupt - cmd52. mmc0: reset 0x2 never completed. mmc0: reset 0x4 never completed. mmc0: internal clock never stabilised. 

know how can decrease sd card clock speed further without causing system failure this?

thanks,

sounds timeout somewhere needs increased - check mmc driver code. but, may mean go out of spec , still may not work.

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